There are several scenarios in which it is desirable to selectively ignite separate units of reactive materials either simultaneously or sequentially depending upon selected variables. For example, in the event of a vehicle crash it would be advantageous if the gas generators used in the activation of various vehicle occupant protection devices, such as airbags and seat belt pretensioners, are actuated by a master control unit communicating with remote device control units located at the gas generators to selectively activate the gas generators in dependence upon various parameters. It would also be advantageous to have similar capabilities for selectively igniting various units of reactive materials, such as explosives, in mining or demolition operations.
One conventional type of system for controlling the initiation of gas generators used in the activation of vehicle occupant protection devices uses a central electronic control unit with a microprocessor. These systems usually have limited means of component failure detection. Another problem with activating the vehicle occupant protection devices directly from a central electronic control unit is that the activation signals are transmitted over hard wires directly to the vehicle occupant portion device. Cable short circuits of the activation signal to the battery voltage or ground could accidentally activate a vehicle occupant protection device. Induced transients and other electromagnetic interference could also have detrimental effects on safety device operation in such a system. Yet another disadvantage of such a system is that additional components must be added to the central electronic control unit as additional safety devices are added to a system. This adds to the space required to accommodate the central electronic control unit in the vehicle.